Piston



Oct. 22, 1929.

Original Filed March 16, 1927 !1Illllillllllllllulllllllllllll4 A. L. NELSON 1,732,414

PISTON j8 ii DD 19 19 11% I I INVENTOR Mae/J Patented Oct. 22, 1929 UNITED STATES PATENT OFFICE .ADOLI'IHI L. NELSON, OF DETROIT, MICHIGAN, ASSIGNOR T BOHN ALUMINUM & BRASS CORPORATION, OF DETROIT, MICHIGAN I rrs'ron Appllcaton filed March 16, 1927, Serial No. 175,647. Renewed March 14,1929.

This invention relates to pistons particutively inexpansible struts to overcome the difliculties due to the high rate of thermal expansion of certain light-weight piston materials, such as aluminum alloys. The present invention aims to utilize the principles heretofore disclosed and to produce an im proved piston by the cooperation of certain novel features of construction hereinafter more fully set forth.

In the drawings:

Fig. 1 is an elevation partly in section of a piston embodying the invention;

Fig.2 is a section on line 22 of Fig. 1;

Fig. 3 is a section on line 8-3 of Fig. 1;

Fig. 4 is an enlarged sectional detail showing a modifiedjoint between a strut end and a bearing portion;

Fig. 5 is a view similar to Fig. 4 showing a further modification.

Referring to the drawings more specifically, the piston, which is preferably formed a of light-weight material, such as an alloy of aluminum comprises a head portion and a skirt portion, the latter term applying to the zone lying below the head.

The piers 10, which depend from the head,

are reinforced internally by ribs 11 and externally by a rib 12, and have the piston pin bosses 13 formed therein. Below the pin bosses the piers connect with the horizontal arcuate webs 14, which are joined to the lower circular part 15 of the skirt. On opposite sides of the skirt and located 90 from the pin bosses, the semi-cylindrical bearing portions 16 and 17 extend upwardly from the circular part 15 of the skirt. These bearing portions are discontinuous from the head and from the upper part of the piers and have homogeneous connections with the piers through the ring 15 and webs 14. The circular portion 15 is reinforced at points directly below the opening 20 which lie between-the piers and the bearingportions. This reinforcing may be accomplished in any convenient manner as by thickening the skirt at these points to form the pads 21.

Piston ring grooves 18 are cut into the side of the piston head, the lowest groove being positioned so. that the slots 19, between the bearingportions 16 and 17 and the head, are

located at the-bottom of this groove.

The skirt is provided with a slot or slots extending upwardly from the lower end thereof as at 22.

A pair of flat, plate-like struts 24 extend between the bearing portions, the struts being located above the axis of the piston pin bosses and inside the piers. Positioning holes 25, formed in the strut, form means by which the strut is accurately positioned and positively held against all movement during the operation of casting.

In casting, the material of the pier is-cast in contact with the outer surface of the strut only, while the ends of the strut are slightly embedded in the material of the bearing portions, the strut ends being so formed that the material of the bearing portions does not' have a cast-in grip on the strut end. This may be done in any convenient manner, three possible constructions being illustrated. Fig. 3 shows rounded dome-like ends 27 Fig. 4 shows angular dome 28, while Fig. 5 shows an Lshaped foot 29 with its corners rounded to prevent the skirt material from obtaining a grip on the foot during the shrinking period after casting. After casting, the material of the piers tends to draw away from the struts, but it is at all times substantially in contact with the struts.

As the piston cools after casting the hearing portions tend to contract toward each other, but the struts hold them out in positions designed to give a certain clearance that will prevent piston slap when the motor is cold, thereby setting up certain stresses in the bearing portions. As the piston warms up during operation the increase in temperature tends to relieve the stresses, but does not cause the bearing portions to expand away from the never as high as the casting temperatures.

The strut does not have a cast-in joint with the bearing portions nor with the pier, and

v hence it transmits less heat from the head to the bearing portions than does a strut with cast-in joints.

The strut is so positioned that there is a space 30 between its lower edge and the piston pin boss, and hence there is no mechanical cooperation between the strut and the pin boss,

the strut serving merely as a spacer between the bearing portions. The strut is kept in proper position solely by reasonof the engagement of its ends in sockets formed in the bearing port-ions.

I claim 1. A piston comprising ahead, piers depending from the head, bearing portions connected to the piers, and a pair of struts extending between the bearing portions and substantially in contact with the piers, the

- ,20 struts being held in place solely by having their endsengaged-in sockets formed in the bearing portions. p

2; A piston comprising ahead, piers depending from the head, bearing portions formed of light-weight material connected to the piers, and a pair of struts of relatively inexpansible material extending between the bearing portions and substantially in contact withthe piers, the struts being held in place solely by having their ends engaged insockets formed in the bearing portions.

'3. A piston comprising a head, piers depending "from the head, bearing portions formed of light-weight material connected to the piers, and a pair of struts of relatively in expansible material extending between the bearing portions and substantially in contact with the piers, the ends of the struts being engaged in sockets formed in the bearing por- 40 tions, the struts having no positive connection either with the piers or with the bearing portions;

4. A piston comprising a head and bearing portions, and a pair of spacing struts extending between the bearing portions, each strut having free surface engagement with both bearing portions, and being held in place solely by having its ends engaged in sockets formed in the bearing portions. 4 In testimony whereof I affix my signature.

' ADOLPH L. NELSON. 

